He failed in finding the job. I think that he _____to get some

more qualifications before applying for the job.

A．should have tried

B．must have tried

C．might have tried

D．needn’t have tried

甲经过数十年的学习、专研和实践成了火箭的成功制造者；而乙未经过专门学习、训练，成了植树工人。则甲和乙的劳动（）

①甲是复杂劳动，乙是简单劳动②甲是简单劳动，乙是复杂劳动

③同等时间内，甲乙创造的价值一样多④同等时间内，甲创造的价值比乙多

A.①②

B.①④

C.②③

D.③④